QQ: Capacitive Sender Wiring

[RV7Factory]

Quick stupid question...

I crimped on the terminals for my capacitive senders, but the instructions also recommend soldering them. In order to solder, I assume it is ok to remove the plastic insulation on the terminal. Ok or not?

[az_gila]

Yes... but cut off the old terminal and use a new one.
You probably won't be able to slide the correct size heat shrink tubing over the existing terminal... and you will need the heat shrink on a soldered joint to take stress off the transition from stiff solder to flexible wire...

gil in Tucson

[RV7Factory]

Thanks Gil! I only have a connector on one end so far, so I can just slide the heat shrink up the wire from the other end.

[dan]

A good crimp is all you need. I would not use heat shrink inside the fuel tank. Keep in mind, we're talking inside the fuel tank here.

)_( Dan
RV-7 N714D (785 hours)
http://www.rvproject.com

[RV8RIVETER]

Soldering is not mil-spec when it comes to primary wiring connections in aircraft. If you have a good ratcheting crimper of proper size you will get the same connection with a crimper. Solder will wick up the wire strands and will make the wire susceptible to fatigue breaking, which is why it is not recommended. Wth the fuel sloshing/waving around, I would think there will be more than a bit if wire movement.

I crimped mine and instead of heat shrink, used Pro-seal to seal and add another layer of mechanical fastening.

If you feel a personal need to solder it anyway, then make sure you fasten the wire securely so that no wire movement is possible in the last 1-2 inches of length. A broken wire in here would not be good thing.

My humble 2 cents.

[Captain_John]

Soldering is fine. It makes a nice, gastight connection.

Crimping is for a mechanical connection. It coincedently makes an electrical connection.

Soldering is for an electrical connection. It coincedently makes a mechanical connection.

Don't apply so much heat as to melt the plastic of the terminal. Here is a pic of mine:



Hope this helps!

CJ

[RV8RIVETER]

While we are free to choose whatever methods we like as builders, I just wanted to make a correction.

Soldering is the standard for PCB's and consumer relctronics, but NOT the standard for commercial or military aircraft.

Crimping is the standard and by mis-spec definition;
"Crimp is the physical compression (deformation) of a contact wire barrel around a conductor to make an electrical and mechanical connection to the conductor"

"The electrical resistance of a properly designed and controlled crimp joint should be equal to, or less than, the resistance of an equal section of wire."

Which are the same electrical characteristics of a properly soldered connection.

[jcoloccia]

In general, there's no reason to ever solder AND crimp anything. A proper crimp is both airtight and at least as strong as the wires you're crimping. The second crimp you add to a crimped joint isn't to keep the joint from falling apart like most people think...it's just to immobilize the wires since the part that's crimped is practically solid and is just as "brittle" as a soldered joint. Adding solder to such a joint will do absolutely no good for "strength" or conductivity (nor will it hurt, typically), and will just increase the likelyhood of making the joint brittle.

A properly soldered and strain relieved joint is just as durable and electrically sound as a crimped joint, and crimping a properly soldered joint will do absolutely no good...in fact it will negatively affect integrity of the joint if anything.

In terms of reliability, it's infinitely easier to make a perfect crimp with a ratcheting crimper than it is to make a perfect solder joint with the best Weller or Hakko money can buy. How do you put a Q/A stamp on a solder joint? Looking at it doesn't work. You have to trust your trained technicians and destructively test samples (yank on them, take cross sections, etc etc). Crimping, on the other hand, is easy to inspect...did he use a calibrated crimper? Yes? *STAMP*.

Personally, I intend to crimp everything I can with a decent crimper because it's pretty much a no-brainer to make a joint that will outlast just about everything else on the airplane.

[osxuser]

I agree that crimping is the way to go.

[Davepar]

If I remember correctly, the other end of the wire gets attached to a coax bulkhead connector at the wing root that has a solder cup. No choice there but to solder. It gets covered with Proseal after that.